An engineer must establish a trunk link between two switches. The neighboring switch is set to trunk or desirable mode. What action should be taken?
An engineer must establish a trunk link between two switches. The neighboring switch is set to trunk or desirable mode. What action should be taken?
To establish a trunk link between two switches when the neighboring switch is set to trunk or desirable mode, the local switch should be configured to actively initiate the trunk negotiation. Configuring the switchport mode as dynamic desirable makes the switchport actively attempt to convert the link to a trunk link. This ensures that the port will become a trunk port if the neighboring port is set to trunk, dynamic desirable, or even dynamic auto mode, thereby ensuring a successful trunk link establishment.
B and C are correct
Yep, either would work. auto <-> desirable = trunk auto <-> trunk = trunk desirable <-> auto = trunk desirable <->desirable = trunk
Actually B is correct as well
B. configure switchport mode dynamic desirable: This command sets the local switchport to negotiate the trunk link actively. It will initiate negotiations if the neighboring switch is set to desirable, and it will accept negotiations if the neighboring switch is set to trunk mode. This is the correct choice in this scenario. C. configure switchport mode dynamic auto: This command sets the local switchport to negotiate the trunk link passively. It will accept negotiations if the neighboring switch is set to desirable mode but will not initiate negotiations. This is not the best choice in this scenario.
When connecting two switches via a trunk link, it's crucial to decide the switchport mode settings. Given that the neighboring switch is set to trunk or desirable mode, you should configure the local switch to a mode that enables successful negotiation. Modes dynamic desirable and dynamic auto will try to convert the link to a trunk link if the neighboring port is set to trunk, dynamic desirable, or dynamic auto. Since the neighboring switch is already set to desirable mode, which actively attempts to convert the link into a trunk, you should configure switchport mode dynamic desirable (option 2). This way, the local switch will also actively attempt to convert the link to a trunk link, which will ensure a successful trunk link establishment as both sides are actively negotiating for it.
its b because auto & auto -> none
If the switch is old model: -Default mode is dynamic desirable and a command wouldn't be needed as it would already form a trunk, this scenario discards B and C. If the switch is new: -Default mode is dynamic auto and it would also form a trunk without the need of an additional command. This discards option C as it makes no sense to issue an existing command and leave the option B. Also the question says "must form a trunk".
good point
I guess that's why they keep saying in Cisco classes that DTP is no longer part of the curriculum. They've been saying that since at least 8y years ago.
you guys how you vote for B and in the question this hint : The neighboring switch is set to trunk or desirable mode ... means we have already desirable mode, the other neighboring must have Auto or Active ... correct me if im wrong
You are wrong. Auto/active/passive stuff are related with EtherChannel LACP and PaGP. Dynamic auto, dynamic desirable, access, trunk are related with trunk mode and access more.
@ Alternative8787. Yeah, you almost got me mixed up as well. The question is more DTP-related, but I see why you would mix it up with EtherChannel. At some point, they do go hand-in-hand. But for this one, set aside the LAG technology for a moment. Stay on the matter at hand.
According to chatgpt is B
Going with B
B is correct auto and auto will not actively form a trunk
b is correct
Summary The table below summarizes the possible states: Port 1 Port 2 Trunk Formed? Trunk Trunk Yes Trunk Dynamic Desirable Yes Trunk Dynamic Auto Yes Trunk Access No Dynamic Desirable Dynamic Desirable Yes Dynamic Desirable Dynamic Auto Yes Dynamic Auto Dynamic Auto No Dynamic Desirable Access No Dynamic Auto Access No Nonegotiate Trunk Yes Nonegotiate Nonegotiate Yes
When a Cisco switch is configured in "desirable" mode for a particular trunk negotiation (trunking) protocol, the state of the other switch must be configured accordingly to ensure a compatible and stable trunk configuration. If a switch is configured as "desirable", this means that it is willing to form a trunk if the other side is also configured to form a trunk (i.e., "desirable", "auto", or "on"). So for best practices: 1. **If both switches are under your control:** - You can configure the other switch in "desirable" mode to ensure that both sides are configured to form an active trunk. 2. **If only one switch is under your control:** - Configure the other switch to "desirable", "auto", or "on", depending on your trunk configuration policy and network needs. - "Desirable" if you want the trunk to be formed whenever possible. - "Auto" if you want the switch to accept trunk formation if the other side is configured to form a trunk. - "On" if you want the trunk to always be formed, regardless of the configuration on the other side. Always ensure that both sides of the trunk link are configured compatible to avoid interoperability issues and ensure network stability.
Although both B and C are correct, I think here the logic here is granting the "least privileges". By setting the switch to dynamic auto it will only form a trunk with another switch set in trunk or dynamic desirable and NOT in dynamic auto (2 conditions, as stated in the question). By setting it to dynamic desirable it will form a trunk with another switch set to desirable OR auto OR trunk (3 conditions)
• Dynamic Auto — Makes the Ethernet port willing to convert the link to a trunk link. The port becomes a trunk port if the neighboring port is set to trunk or dynamic desirable mode. This is the default mode for some switchports. • Dynamic Desirable — Makes the port actively attempt to convert the link to a trunk link. The port becomes a trunk port if the neighboring Ethernet port is set to trunk, dynamic desirable or dynamic auto mode. B and C are correct
Both answers are correct very confusing: switchport mode dynamic desirable: Makes the interface actively attempt to convert the link to a trunk link. The interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode.
Trunking Mode Neighbor Mode Resulting Behavior Trunk Trunk Trunk link is established Trunk Access Trunk link is established Trunk Dynamic Auto Trunk link is established Trunk Dynamic Desirable Trunk link is established Access Trunk Trunk link is established Access Access Access link is established Access Dynamic Auto Access link is established Access Dynamic Desirable Access link is established Dynamic Auto Trunk Trunk link is established Dynamic Auto Access Access link is established Dynamic Auto Dynamic Auto Access link is established Dynamic Auto Dynamic Desirable Trunk or access link is established Dynamic Desirable Trunk Trunk link is established Dynamic Desirable Access Access link is established Dynamic Desirable Dynamic Auto Trunk or access link is established Dynamic Desirable Dynamic Desirable Trunk link is established I think Answer B is more convincing to me